def commonNGrams(cnnurl, p, N=30, bn=12):
article_ngrams = stats.mostCommonNGramsFromString(art.articleTextFromURL(cnnurl),10)
if p == None:
p = posts.getPostsFromUrl(cnnurl)
common_ngrams = stats.mostCommonNGramsFromPosts(p,N)
bigrams = filter(lambda x: x[0] not in article_ngrams[1], common_ngrams[1])
unigrams = filter(lambda x: x[0] not in article_ngrams[0], common_ngrams[0])
bigrams = bigrams[0:bn]
# fake reweighting by multiplying the bigram counts by a constant
bigrams = map(lambda x: tuple([x[0], x[1]*3]), bigrams)
unigrams = unigrams[0:(N-bn)]
common_ngrams = unigrams
common_ngrams.extend(bigrams)
common_ngrams = stats.nGramsListToTokenStringsList(common_ngrams)
return common_ngrams
